Abstract: An articulated rotor system with a servo-flap rotor control system locates the focal point of a blade retention spherical elastomeric bearing inboard of a joint in the servo-flap pitch control tube which separates the flap hinge and supports the servo-flap pitch control tube on a single pivot bearing within a blade retention spindle. Rotor blade flapping produces relative movements between the servo-flap pitch control tube and the blade retention spindle which is converted through a servo-flap drive linkage into servo-flap pitch motions to provide flap/pitch coupling which reduces steady and transient blade flapping.

Abstract: An electrically heatable elastomeric bearing according provides an electrically heatable elastomeric bearing shim layer which replace one or more of the metallic shims currently used in non-heatable elastomeric bearing designs. The heatable shim layers facilitate the maintenance of a constant bearing spring rate to prevent an increase to bearing loads and reduced strength that may otherwise occur at cold temperatures.

Abstract: A composite lug assembly includes a composite lug defining a loaded side and an unloaded side and having at least one hole extending therebetween, a shoulder bushing assembly including a first side bushing having a first cylindrical portion adapted to fit in the hole and a first shoulder portion extending from the first cylindrical portion and a second side bushing having a second cylindrical portion adapted to fit within the first cylindrical portion and a second shoulder portion extending from the second cylindrical portion wherein the first side bushing is made of a different material than the second side bushing.

Abstract: A rotor blade assembly system includes a trim tab assembly which utilizes relatively thick resilient members bonded between a trim tab and the two trim tab doublers. Spanwise segmenting of the tab and the use of thick resilient member isolates the trim tab from normal strain. Because the trim tab is made of aluminum, the tab can be readily adjusted the field using a conventional tool.

Abstract: A snubber inner member has a doubly convex outer surface portion having a central longitudinal axis. A shim/spacer stack secured to the outer surface portion couples the snubber inner member to the second member. A retainer having one or more engagement surfaces cooperates with one or more engagement surfaces of the snubber inner member to constrain lateral movement of the snubber inner member relative to the retainer while permitting longitudinal movement of the snubber inner member away from the retainer. An elastomer secures the retainer to the first member.

Abstract: A rotor blade assembly system includes a trim tab assembly which utilizes relatively thick resilient members bonded between a trim tab and the two trim tab doublers. Spanwise segmenting of the tab and the use of thick resilient member isolates the trim tab from normal strain. Because the trim tab is made of aluminum, the tab can be readily adjusted the field using a conventional tool.

Abstract: A snubber inner member has a doubly convex outer surface portion having a central longitudinal axis. A shim/spacer stack secured to the outer surface portion couples the snubber inner member to the second member. A retainer having one or more engagement surfaces cooperates with one or more engagement surfaces of the snubber inner member to constrain lateral movement of the snubber inner member relative to the retainer while permitting longitudinal movement of the snubber inner member away from the retainer. An elastomer secures the retainer to the first member.

Abstract: A flexbeam rotor system includes an intermediate tube and a torque tube that envelopes a flexbeam in spaced relation thereto. The torque tube is connected to the flexbeam at its radially outer end and articulately connected to the intermediate tube through a snubber-vibration damper system. The torque tube is connected with an aerodynamic rotor blade member. The snubber vibration damper system includes a snubber bearing and an independent lead/lag bearing. The snubber bearing is located between the flexbeam and the intermediate tube along a pitch change axis. A lead/lag bearing is mounted between the intermediate tube and the torque tube on both the leading and trailing portion of blade assembly. Pitch/lag coupling complications are minimized as lead/lag motion takes place between the torque tube and the intermediate tube. As lead/lag motion is accommodated in the independent lead/lag bearing, the snubber bearing is of a greatly reduced height in relation to conventional design.

Abstract: A multi-focus elastomeric bearing system provides a plurality of hemi-spherical bearings arranged in series. An inner hemi-spherical bearing rotates about a focal point which is X distance above a pitch change axis while an outer hemi-spherical bearing rotates about a focal point which is X distance below the pitch change axis. The bearing system thus has an effective rotational center along the pitch change axis. The inner hemi-spherical bearing has a greatly reduced radius and high wrap-around angle, while the outer hemi-spherical bearing has an increased radius and reduced wraparound which provides a more requirement tailored bearing system.

Abstract: A flexbeam rotor system includes an intermediate tube and a torque tube that envelopes a flexbeam in spaced relation thereto. The torque tube is connected to the flexbeam at its radially outer end and articulately connected to the intermediate tube through a snubber-vibration damper system. The torque tube is connected with an aerodynamic rotor blade member. The snubber vibration damper system includes a snubber bearing and an independent lead/lag bearing. The snubber bearing is located between the flexbeam and the intermediate tube along a pitch change axis. A lead/lag bearing is mounted between the intermediate tube and the torque tube on both the leading and trailing portion of blade assembly. Pitch/lag coupling complications are minimized as lead/lag motion takes place between the torque tube and the intermediate tube. As lead/lag motion is accommodated in the independent lead/lag bearing, the snubber bearing is of a greatly reduced height in relation to conventional design.

Abstract: A novel apparatus and method are provided to reduce the interlaminar shear loading in the retention area of composite springs used in a vibration isolator for use with a helicopter main rotor. The composite springs, which are made of a graphite laminate, are weakest when subject to inter-laminate shear. The shear forces are highest during bending and twisting about the longitudinal axis of the laminate composite. The invention consists of several techniques to minimize the inter-laminate shear. The first is the use of nylon mounting pads which are attached to the ends of the graphite laminate spring arm at the locations where mounting to the inner and outer hubs is to take place. In particular, it has been found that the nylon spacer must be recessed back from the perimeter edges of the graphite spring arm the same distance which is approximately equal to the width of the graphite spring arm.

Abstract: A vibration isolator (20) operative for reducing vibration active on a main rotor (12) of a rotorcraft. The vibration isolator (20) includes a hub attachment fitting (22) secured in combination with the main rotor (12) and a spring-mass system (24) mounting to and rotating with the hub attachment fitting (22). The vibration isolator (20) is characterized by the spring-mass system (24) having a fairing (44) operative to aerodynamically contour the spring-mass system (24) while providing a portion of the working mass thereof. Other features of the vibration isolator include adapting the hub attachment fitting (22) to accept hub-mounted rotor systems (36), provide access to the rotor hub mounting attachment (34), and provide a motion limiting portion (74) for reducing loads acting on the spring-mass system (24).

Abstract: An inertial mass (50) for a vibration isolator (20) having an attachment fitting (22) adapted for rotation about an axis (16) and a spring (40) adapted for rotation with the attachment fitting (22). The inertial mass (50) is characterized by a pair of segments (52) each having a generally Z-shaped cross-sectional configuration. More specifically, each segment (52) defines a central web (54), a first leg (56) projecting radially inboard of the central web (54) and a second leg (58) projected radially outboard of the central web (54). The first and second legs (56, 58) are integral with the central web (54) and the second legs (58) are adjoined along a mating interface (I) to define the assembled inertial mass (50). As assembled, the inertial mass (50) is adapted for being mounted in combination with the spring (40) of the vibration isolator (20).

Abstract: An optimized composite flexbeam (10) having a plurality of adjoining regions including a hub attachment region (HAR), a blade attachment region (BAR), a pitch region (PR), an outboard transition region (OTR) disposed between and adjoining the pitch region and blade attachment regions (PR, BAR), and an inboard transition region (ITR) disposed between and adjoining the pitch and hub attachment regions (PR, HAR). The inboard transition region (ITR) includes a first transition subregion (ITR-1) and a second transition subregion (ITR-2) wherein the second transition subregion (ITR-2) defines a width conic and a critical width transition subregion (CR.sub.wt). Furthermore, the first and second inboard transition regions (ITR-1, ITR-2) are composed of a combination of unidirectional and off-axis composite materials (U, O) wherein the off-axis composite material (O) defines a percentage %O of off-axis composite material (O) and wherein the percentage %O in the critical transition subregion (CR.sub.

Abstract: An optimized composite flexbeam (10) having a pitch region (PR) which includes a core laminate (50) of unidirectional fiberglass material (U.sub.F), and face laminates (52) of unidirectional graphite material (U.sub.G) bonded to mating surfaces (50.sub.M) defined by the core laminate (50). The core laminate (50) and face laminates define an aspect ratio which is greater than or equal to 10 and define chamfered edge surfaces (54.sub.S). Each chamfered edge surface (54.sub.S) defines a critical acute angle .alpha. with respect to the flapwise bending neutral axis (X.sub.A) of the pitch region (PR) and defines a lateral edge (54.sub.E) disposed a vertical distance X from the flapwise bending neutral axis (X.sub.A). The critical acute angle .alpha. is between about 14 degrees to about 22 degrees and the vertical distance X is about 12.5% to about 37.5% of the pitch region thickness dimension (T.sub.PR).

Abstract: A mounting assembly (50) for mechanically interconnecting a helicopter rotor blade (12) to a rotor hub assembly (10) and for mechanically interconnecting the rotor blade (12) to a damper assembly (52) and a pitch control input assembly (54). The rotor hub assembly (10) includes a hub plate (16) having a hub plate aperture (22) for mounting a rotor assembly yoke (24). The rotor assembly yoke (24) includes upper and lower radially extending arms (28a, 28b) which are disposed above and below the hub plate (16) and which include a set of mounting apertures (29) formed through the proximal end thereof. The mounting assembly (50) includes upper and lower clevis arms (60a, 60b) formed at the root end (56) of the rotor blade (12), a horn/damper fitting (64) interposed between the upper and lower clevis arms (60a, 60b), and upper and lower spacer plates (90a, 90b) disposed between the clevis arms (60a, 60b) and the radially extending arms (28a, 28b) of the rotor assembly yoke (24).

Abstract: A mounting assembly (100) is provided for securing a helicopter snubber bearing (70) to a bearingless rotor assembly (10) which includes a flexbeam connector (22) mounted to a torque drive hub member (18). The mounting assembly (100) includes a retainer fixture (102) for mounting a retainer (104) which engages an inner bearing race portion (88) of the snubber bearing (70). The retainer fixture (102) is mounted to the flexbeam connector (22) and includes an inboard end portion (112), a restraint portion (114) extending radially outboard thereof, and a seat portion (116) disposed therebetween. The retainer (104) is disposed in register with, and is compliantly bonded to, the seat portion (116) of the retainer fixture (102), and furthermore abuts the restraint portion (114) which provides redundant retention therefor.

Abstract: A pitch adjustment assembly (100) for a bearingless rotor assembly (20) which includes a torque tube member (36) enveloping a flexbeam connector (22), which torque tube member (36) defines a geometric center (120) and is operative to impart pitch motion to the rotor blade assembly (20).

Abstract: A hybrid composite flexbeam for a soft inplane bearingless main rotor assembly has eight spanwise regions: a hub attachment region; a first tapered region; a second tapered region; an inboard transition region; a pitch region having a cruciform configuration; an outboard transition region; a tapered outboard transition region; and a main rotor blade, torque tube attachment region. The pitch region is formed from unidirectional fiberglass plies, a 50/50 admixture of unidirectional fiberglass and graphite plies, and unidirectional graphite plies, all of which extend from root to tip of the hybrid flexbeam. Unidirectional fiberglass and graphite plies of varying lengths are interleaved in the second inboard tapered region. Fiberglass and graphite cross plies of varying lengths are interleaved in the first inboard tapered region. Fiberglass and graphite cross plies and unidirectional fiberglass plies of varying length are interleaved in the outboard tapered region.

Abstract: A flexbeam for a soft inplane bearingless main rotor assembly has six spanwise regions: a hub attachment region; a first tapered region; a second tapered region; a pitch region; a tapered outboard transition region; and a main rotor blade, torque tube attachment region. One described embodiment of the flexbeam is fabricated from continuous unidirectional fiberglass plies having a 0.degree. fiber orientation, unidirectional fiberglass plies of varying lengths having a 0.degree. fiber orientation, and graphite cross plies having .+-.45.degree. fiber orientations. The pitch region is formed solely by the continuous fiberglass plies which define a rectangular cross section therefor. The second tapered region is formed solely by the continuous fiberglass plies and the fiberglass plies of varying lengths. The ends of the fiberglass plies terminate in a distributed arrangement in the second tapered region to define the taper thereof.